Liverpool could face expulsion from the Carabao Cup if they are found to have fielded an ineligible player against MK Dons on Wednesday.
The EFL is investigating the third-round win, in which Liverpool fielded four teenagers in the starting line-up.
Sanctions could range from a fine to being ejected from the cup. Liverpool face Arsenal in the next round.
“The club are aware of a potential administrative issue pertaining to one of our players,” a club statement said.
“We are working with the relevant authorities in order to establish the facts of the matter and will be making no further comment until this process is complete.”
The EFL added: “We are currently considering the matter.”
The identity of the player in question has not been disclosed.
In 2014, Sunderland were fined by the Premier League and the EFL after they fielded an ineligible player in four league matches and a League Cup match.
The club admitted they made an administrative error with striker Ji Dong-won but were not deducted points or kicked out of the cup.
Liverpool beat MK Dons 2-0 thanks to goals from James Milner and 17-year-old Ki-Jana Hoever, and are set to host Arsenal at Anfield in the week commencing 28 October.